7. Conclusions and further developments
All the flexible models show performance results that are very close to the rigid models.
The flexible beam model provided requires a large amount of memory, and the time to run a simulation is longer compared to the correspondent rigid model. The flexible mnf model is easier to set up and run compared to the first approach. It shows similar computational time compared with the equivalent rigid model, even if it needs further investigation to be tuned properly.
At the moment it is not possible to study the effect of a complete mnf model with nose, left and right flexible Landing Gears unless the other parts are available.
Simulations demonstrate that there is not a great sensitivity when flexibility is taken into account from a Turning Radius and Turn Width point of view. Tyres Side Forces are very sensitive when introducing flexibility, in particular when the strut is flexible.
Torque depends mainly from the tyre forces, hence shows a great sensitivity when flexibility is introduced in the model.
The computational time is a highly sensitive parameter when there is flexibility; it depends from the complexity of the model.
In case of requests with different aircraft configurations coupled with several types of manoeuvre at different speed, the number of run can be very high; in this case the time to complete each run is an important parameter in the decision between rigid and flexible model.
The third approach has to be further developed; it is a new model using the lessons learnt from the several mnf configurations and integrating the beam model idea from the A350XWB-900 supplier model. It has not been refined for lack of time.
From a ground manouvreability point of view, when a clearance check or an airport compatibility is requested, the current rigid models give good results and are easier to set up compared to the flexible models investigated during
this thesis. Hence for ground manouvreing simulations it is advisable to use the rigid model as currently done in ELYD.
Further developments include a flex beam sidestay along with a beam main fitting in order to improve the third approach model described in chapter 5. Moreover once that ADAMS/View 2011 will be available, it will be easier managing mnf files within this multibody simulation tool. A new feature is introduced in the new release and it would be possible to flip the left main fitting and obtain the right Main Landing Gear. Thus the aircraft model would have both left and right flexible mnf Landing Gears and the results would be more robust.
Therefore it will be possible developing the mnf parts model in ground manoeuvring simulations.
Previous studies within Airbus investigated about a flexible mnf fuselage. Using ADAMS 2011 it will be possible to understand better the behaviour and complexity to a higher level. It will be possible to integrate the flexible mnf fuselage in the flexible mnf Landing Gear model and refine this approach.
Bibliography
[1] Internal Team Wiki, ELYD, Airbus Operational Ltd., 2011 [2] MSC.SOFTWARE CORPORATION, Online help
homepage: www.mscsoftware.com, 2011
[3] QTRMICH25/04pB, Michelin Qualification Test Report, Ref. MICH25/04 Issue 3, 2005 (internal document)
References
x Negrut, D. and Harris, B.: ADAMS theory in a nutshell Script, Department of Mechanical Engineering, University of Michigan, 2001 x Airbus A320 Aircraft Technical Description, ATD Vol. 1 - General,
Issue 4, March 1999, Airbus Industrie (internal document)
x Bjoern Kirchhoff, Diploma Thesis: A study of the effects of aircraft flexibility and shock absorber characteristics during ground manoeuvres by simulation, University of Technology Hamburg, Airbus Operations Ltd, 2006.
x Norman S. Currey, Aircraft Landing Gears Design: Principles and Practices, AIAA Education Series, 1988.
